The experiments represent the continuation of an ongoing research program aimed at identifying the cellular targets of an injury-induced (sprouted) projection in the mammalian hippocampal formation and to investigate the biological mechanisms(s) which underly this sprouting response. The research plan includes experiments designed to: 1) identify the synaptic targets of sympathohippocampal fibers using electron microscopic techniques, including HRP histochemistry, autoradiography, and degeneration studies 2) test the hypothesis that hippocampal mossy fibers are the source of the putative growth factor released upon septal deafferentation by studying whether sympathetic sprouting will occur in the regio superior of rats, following the lesion-induced growth of mossy fibers into this area, and 3) test the hypothesis that the hippocampal growth activity, which we have recently found to increase in response to medial septal and entorhinal lesions, is related to NGF and is involved in sympathetic and septohippocampal sprouting. There should not be insurmountable technical or theoretical problems which would prevent the acquisition of useful information on the biology of injury-induced neuronal rearrangements and its possible involvement in recovery of function following injury to the CNS.